Hydraulic windshield wiper



ugflO, 1948. H. E. RosE 2,446,611

HYDRAULIC WINDSHIELD WIPER 5 sheets-sheet 1 Filed Nov. 30, 1942 @w1/W, Kawa m Aug 10,1948. H. E. ROSE 2,446,611

HYDRAULIC WINDSHIELD wIPEn I 5 Sheets-Sheet 2 Filed Nov. 50, 1942 30/ 49 /A//EA/roe:

How/12D E. F055' ug. 1G, 1948.

Filed Nov. 30, 1942 5 Sheets-Sheet 3 /A//EA/roe.' fawn/2D E. POSE,

Aug. 10, w48. H. E. ROSE` 2,446,613

HYDRAULIC WINDSHIELD WIPER Filed Nov. 50, 1942 5 Sheets-Sheet `4 m// Ww# @www w Z Z @7% ww www f w www C 3 MM 1 d m v fm t, Uf ww w l M Aug.' E0, 1948. H. `ELROSE 4l-W961i HYDRAULIC WINDSHIELD wIPER Filed Nov. 5o, 1942 5 Smets-sheet' 5 Patented Aug. 10, 1948 HYDRAULIC WINDSHIELD WIPER Howard E. Rose, Normandy. Mo., assigner, by mesne assignments, to Kcartott Company. Inc., New York, N. Y., a corporation of New York Application November 30, 1942, Serial No. 467,359

23 Claims.

The present invention relates to hydraulic windshield wipers.

In general, it comprises one or more operating umts, a control valve adapted to be connected to a source of hydraulic ilow and a return thereto. The valve is one that is reversing, so that the wipers are operated rst in one direction and then in the other.

An object oi the invention is to provide a mechanism of this kind in which a cut-R valve may be used and which relieves the entire system from pressure when th'e mechanism is stopped.

A further object is to provide a mechanism of this kind in which each blade of the wiper may be installed without interfering withv the operation of the other blade. It is also an object to provide synchronization of the blades so that they operate togethenand to provide resynchronization in case one or more oi them is blocked to destroy synchronization temporarily.

A further object is to provide a mechanism of this kind in which reversal may occur without completion of th'e stroke. In this connection, a further objectis to provide 'a mechanism in which both blades will operate even though one is 11mited in its stroke.

A further object is to provide a mechanism oi this kind embodying a plurality or blades which may wipe in the same or in opposite directions.

A further object is to provide a mechanism in which the several units may be disposed .in any desired relationship and operated through a connection of any length or shape.

A further object is to provide a mechanical locking mechanism, automatically released. for holding the blades inan end position when inoperative.

An overall object is to provide a pressureresponsive windshield wiper mechanism in which various elements of the cycle are determined by fluid pressure in the system.

In the drawings:

Fig. 1 is an overall view of the mechanism as it would be connected to a typical installation;

Fig. 2 is an end view of one of the windshield units as on the line 2-2 of Fig. 1;

Fig. 3 is a medial section of one of the windshield units taken on the line 3-3 of Fig. l;

Fig. 4 is a rear elevation of one of the windshield units taken on the line 4-4 o1' Fig. 1;

Fig. 5 is a medial longitudinal section of one of the windshield units taken on the line l-B of Fig..2:

Fig. 6 is a view similar to Fig. 5, but with' the operating piston shown in a dlil'erent position Fig. 7 is a transverse section through one of the windshield units taken on the line 'i--l of Fig. 5;

Fig. 8 is a plan view of the operating control valve, or motive unit as it appears in Fig. 1 and taken on the line 8-8-thereof;

Fig. 9 is a section through the control valve taken on the line 9-9 of Fig. 1;

Fig. 10 is a section through the control valve taken on the line iiil0 of Fig. 1;

Fig. 11 is a section through the control valve taken on the line i I-I I of Fig. 1;

Fig. 12 is a vertical view from the right-hand side of the control unit in Fig. 1 taken on the line i2-I2 thereof;

Fig. 13 is a vertical view oi the control valve looking from the left-hand side of Fig. 1 on the line |31I3 thereof;

Fig. 14 is a bottom view of the control valve taken on th'e line M-M of Fig. 1;

Fig. 15 is a vertical section through the control valve taken on the line iii-i5 of Fig. 1 on the left-hand side thereoi;

Fig. 16 is a vertical section through the control valve' at the right-hand side thereof on the line iB-i of Fig. 1;

Fig. 17 is a vertical section through' the control( valve taken on the line i'l-Il of Fig. 8;

Fig. 18 is a medial vertical section through the control valve taken on the line i8-I8 of Fig. 8;

Fig. 19 is a section through the control valve taken on the line i9l 9 of Fig. 8; Fig. 20 is an enlarged view ot one of the wiper unit slide valves;

Fig. 21 is a section on the line 2i-2l of Fig. 5; and, f

Fig. 22 is a diagram showing the connections to l illustrate the operation. A

In the description of the drawings, certain views have been described as vertical sections or horizontal sections for convenience, since it is not intended to limit the positioning of the mechanism.

In general, the mechanism comprises one or more windshield units, two being here shown at 30 and 3|. The mechanism also includes a-motive unit or control valve 32. A line 33 is connected to a. hydraulic pressure line through an adjustable cut-oli or speed control valve 34. A return line 35 is likewise connected to the hydraulic system. vThis return line runs to a T 36 from which one branch 3l is connected into the control valve 32. and the other branch 38 extends to another T 38 from which the branches M and 4i are piston and thus locate connected into the windshield units 88 and 8|, respectively.

Two lines 42 and 48 lead from the control valve 82 to the wiper'units 88 and 8|, respectively. The two lines 42 and 48 are alternatively pressure and exhaust lines. The two uni nected by a line 44. 1

The windshield units are identical, and Figs. 2 to may be either one of them. For convenience in the following description, it will be assumed that Fig. 5 represents the wiper unit 88. This unit includes a housing 48 through which extends a cylinder 48. A head 88 is attached to one end and a head 8| to the other end. The head I8 receives the line 48 and the head 5| receives the line 44 so that the two lines 48 and 44 are put into communication with opposite ends of the cylinder. The cylinder head 88 has a reduced circular 4cut-out 82 in it and a similar cut-out 88 is found in the head 8|. A small port 84 in the cylinder head 88 terminates in a valve seat 88 that receives a ball valve 86. This ball valve constitutes a check valve as will appear. In the head 5|, there are a similar port l1, a seat 58, and a ball valve 89.

Reciprocable within the cylinder 48 is a piston 88. This piston has a rack 8| on its upper surface that engages with a gear 62 mounted on a shaft 88 to drive the windshield wiper W back and forth.

I'he Vpiston is symmetrical about its center transverse section. At one end.' it is cut away to provide a small head portion 81 having a loose fit with the cut-out 52 in the head 58. A corresponding portion 88 cooperates with the cut-out l8in thehead 8|.

The cylinder has an opening running from one end to the other thereof. This opening is threaded at each end to receive plugs 18 and 1|. These plugs are ported at 12 and 18, respectively. The piston opening at its middle portion has a reduced portion 14 to receive a slide valve 15. The valve 18 is not ported, butfrom its left hand in Fig. 5, it has two opposite nats 18 extending more than half the distance across `the reduced part 14 of the piston. At right angles to the ilats 18 are similar flats 11 extending from the right-hand end of the piston. See Fig. 20.

Springs 88 and 8| act against the two plugs 18 and 1|. At their inner ends, these springs bear against spiders 88 and 84v engaging against the ends ofthereduced portions 14. These spiders admit oil freely past them and into the flats 18 and 11. The spiders 88 and 84 shoulder in the the valve in a central position.

'I'he piston 68 is provided with a relief groove 88, into which are disposed two notches 81 and 88 on its lower side. These are adapted to be engaged by a cup-like plunger 88, and, as will appear, will retain the wipers in their rest positions. The plunger 88 is urged into engaging position by a spring 88 abutting against a fitting 8| that receives the exhaust line 48. The piston 88 operates within a cylindrical Opening The upper portion of the cylinder 82 is connected with two lines 88 and 84. Line 88 leads to a ball-type check valve 85, from which a port 88 extends for communication with the left end of the main cylinder 48 of communication is limited to such times as a notch 81. in the piston 88 registers with the port 86. Similarly, the port 84 communicates with the ball-type check valve 88 opening into a port 88 that may register with a notch |88 in the other end of the piston.

During-operation. when hydraulic nuid is ad- 82 in the housing 48.'

88 and 8| are conheaded by a cap |8I.

against the mechanism stopping on a dead center mitted through the line 44, it will create a pressure against the right-hand end of the piston. displacing the piston until it is stopped either at the end of its normal stroke or prior thereto.- After such stopping of the piston, the pressure will build up against the right-hand end vof Ithe valve 18 and displace it or not, depending upon the other wipers position. As the pressure builds up through the notch |88, bali-type check valve and maintain the locking piston 88 down against the spring 88. Upon a subsequent reversal of the oil ilow, while under pressure, it will be introduced through 'the line 48 andthe notch 81 and maintain the piston back in the same manner.

The control valve or wiper motive unit 82 is connected with the pressure intake line 88 and the exhaust line 81. The control 82 comprises three valves within the housing (Fig, 18). They are the selector valve ||8, the pilot valve III. and the directional valve ||2. These three valves cperate within cylinders ||8, ||4, and ill. respectively.

The pressure line 88 communicates with a port H8 that extends downward through the housing to the level of the cylinder H5.

The port I|8 communicates with the cylinder ||8 through a cross port |I1. It communicates with the cylinder ||4 through a cross port ||8 (Fig. 10). It communicates with the cylinder IIS through a cross port ||8 (Fig. 11). For convenience in manufacture. the ports and ||8 are drilled in from the back of the housing. whereas the port ||8 is drilled in from the front of the housing.

It will be seen, therefore, that pressure is at all times supplied to the several cylinders.

The valve ||8 has three reduced sections |22. |28, and |24, the sections being divided by suitable enlargements on the valve that seal with the cylinder walls. The port ||1 leads into the section |28 of the valve which, in the positions of Figs. 9 and 18. has no outlet.

The fluid under pressure through the portion ||8 (Fig. 16) leads into the cylinder ||4 under control of the valve This valve has two reduced sections |25 and |28 separated by enlarged sections sealing with the cylinder walls.

The pressure through the line 8 (Fig. 11) leads to the cylinder ||5 where it is under control of the valve 2. This valve has two reduced sections |21 and |28 separated by enlarged portions sealing with the cylinder walls.

The directional valve ||2 is normally urged to one extreme position by a, light coil spring |88 This is provided to insure position.

From the cylinder i I5 of the valve I2 (Fig. 1l) there extends a port |88 leading hackwardly to a vertical port |86. The port |86 (F159) connects by a horizontal port |31 with a pressure chamlier at the right-hand end of the selector valve Similarly (Fig. 11) the cylinder IIB on the left of its midsection has a horizontal port |48 leading to a vertical port |4| that communicates with a the mechanism. This horizontal port |42 V(Fig. posite end of the valve I8.

The valve ||8 is designed to rest in a neutral 9) leading to the opposition, which position is shown in Figs. 9, 18,

and 21. Toproduce this, the valve ||8 has an extension |45 at one end, having a nut |48 threaded thereon. .The extension |45 at its cpposite ends has ported washers4 |41 and |48 be it will ilow past the has a chamber |5| within it to receive iluid pressure. It will be seen that the uid pressure from the port |31 can pass into the chamber |5| as well as the chamber around the spring |43, and may act to displace the valve to the left in Fig. 9. Similarly, pressure through the ports |4| and |42 may act against the other end of the valve to displace it to the right. Upon relief of such pressures, the valve will return to its neutral position under the action of the spring |49. The port |38 (Fig. 1'1) is likewise connected to the line 43 and the port |4| is connected to the line 42.

It may be seen from the foregoing, that when oil under pressure ows through the line 33, through the port I6 and the port I i9 to the valve space |28 of the directional valve H2, it may then iiow through the port |35 to the port |36. From the port |36, it ows downwardly through the line 43 to the Windshield units and upwardly tor the port |31, whence it may displace the selector valve ||0 to the left in the views, under condi.`

, seen that when the selector valve is moved from the left of its neutral position. ports |12 and |51 are brought intoregistry: and when the valve ||0 moves to the right, the ports |55 and |13 are brought into registry.

Operation First, the operation of the control valve will be set forth, for which purpose reference is made to the diagrammatic showing of Fig. 22. Assuming that the several valves are in the positions of Fig. l22. and that the main speed control valve 34 (Fig. 1) is open, oil under pressure will ow through the tube 33 and the port ||6 of the control valve.y From the port ||6, it will ow to the space |23 of/the valve ||0. This will have no eilect because it is balanced and no outlet ports are open, the valve ||0 being in its neutral position. Likewise, it will ow from the port |6 into the space |26 with the valve in the position shown. From the space |26, it will flow through the restricted port |58 into the right-hand end of the cylinder to maintain the valve ||2 to the left. This has no immediate effect because the valve is already in such position.

The oii from the port ||6 will likewise ilow through the port ||3 (Fig. 11) where it is admitted to the space |28 by the valve ||2, as the latter is in its left-hand position. From the space |28, it ilows out the port |35 to the tube 43 and to the wiper elements to operate them as will be described. It, likewise, flows upwardly in the port the reduced portion |25 of that valve to bring the pressure port ||8 (Figs. 10 and 18) into communication with a port |56 leading to the left of the directional valve ||2. The port |56 is restricted so as to delay this last action and, therefore, to delayV displacement of the directional valve I2 to the right.

A corresponding port |51 (Fig. 18) leads from the valve ||0 to the right-hand end of the valve I I and a restricted port |58 leads from the valve to the right-hand end of the valve ||2.

In order to exhaust the-several ports and chambers, the exhaust line 31 communicates with a port |62 passing vertically down in front of the valve (Fig. 16). The port |62 at its bottom (Figs. 11 and 16) communicates with a port |63 leading to the cylinder ||5 of the valve ||2 in such wise that when the valve I|2 is to the right, the portion |26 will put the port |35 in communication with the port |63 and out of communication with the pressure port 9.

There is a corresponding exhaust port |64 extending down the other side cf the iront of the valve. It has a corresponding cross port |65 leading into the other end of the cylinder ||5 of the valve ||2. v

Similarly (Figs. and'V 18), the port |62 communicates with the cylinder ||4 through a port |66; and the port |64 likewisecommunicates with this cylinder through a cross port |61 (Fig. 10). As shown in Fig. 10, the portion of the pilotvalve may produce registry between the port |56 through which the uid operates the directional valve I I2. and the port. |61. Similarly, opposite placing of the valve will cause registry between the port |58 and the port |66.

The two ports |62 and |64 are put into communication through a cross port |10 that is here shown as being disposed at the level of Fig. 10.

Likewise, in Fig. 9, the port |62 communicates through a port |12 with the cylinder ||3 of the selector valve ||0; and the port |64 communicates therewith through a port |13. It will be |36 to the right end of the cylinder ||3 until it attains sufiicient pressure to displace that valve to its left-hand position. The spring |43 will prevent displacement of the valve ||0 until the line 43 has become illled with oil. and a pressure is built up in the line 43, as will appear.

It will be seenfrom the foregoing that a pressure is supplied to the line 43 by the foregoing operation. It will now be shown how the valve reverses itself.

When the valve ||0 is moved to the left, it opens the line ||6 to the, port |55 through the space |23. Thereupon, pressure flows readily 1 through the port |55 to dislodge the valve to the right. At the same time, the oil at the opposite end of the cylinder ||4 may move backwardly through the port |51, which, now through the space |24, exhausts into the port |62 through the space |24 and the exhaust tube 31. Thus, the application of pressure to one end of the valve |||`and the relief of pressure at the other end is simultaneous.

As soon as the valve is displaced to the right, the port ||6 is put into communication with the restri-cted port |56 Which causes the directional valve ||2 to begin the move to the right. At the same time, the port |58 is put into communication with the exhaust port |62 through the space |26 on the valve As the described action of the vvalve |2 occurs, the pressure inlet port ||6 is shifted from the space |28 to the space |21; and through the space |21, oil under pressure flows to the port |40, thus applying pressure to the tube 42 that leads to the windshield units, and to the passage |4|. At the same time, the line 43 and the portv |36 are connected to exhaust line |62 through the space |28 7 by it locks the valve. I II in the position previously assumed, because both of the ports |85 and |51 are cut ci! when the valve Ilo is in neutral position. The spring pressure produced upon the selector valve I l is greater than the normal unit operating pressure of the valve and the mechanism. Thus. as'previously noted. 'the selector valve I I o will not shiitbeyond its neutral position until resistance has been built up in whichever o! tubes 42 and 43 is the pressure line. and the pressure thereby admitted to one. ofthe other ends o! the valve IIIl exceeds the setting of the spring |40. The delay through the restricted passages IBI and |58 insures that the valve III will have moved its full stroke before the` valve II2 may move so far as to relieve the pressure holding the valve I I 0. Thus, before the valve I I returns to neutral position, the valve III will be all the way over, insuring admission of pressure to the valve II2 regardless of a return ci the valve I I0 to neutral position. This eliminates the necessity oi a mechanical snap action on the valve I-I2.

Upon the application oi' pressure to the port I 4I and the tube 42 to reverse the wiper mechanisiris.v when a predetermined resistance is reached in the tube'42 and the port I 4 I, this pressure acting through the port |42 (Fig. 9) will act to reverse the selector valve IIIl and thus reverse the cycle previously given.

From the foregoing, it'may be seen that the tubes 42 and 43 alternately become pressurel and relie! lines. It will further be seen that, if either one is a pressure li-ne, itvwill remain'so until the pressure within it attains and exceeds the predetermined value, when a reversal will occur. This insures that pressure will be maintained to the end of the stroke of the windshield wipers because, as will be shown, under normal operating conditions only then can the pressure build up in the pressure. line to exceed minimum required' for shifting the valve IIU. This valve, therefore. is pressure-responsive and cooperates with pressure conditions in the wiper units themselves.

The action of the windshield wiper units will now be described.

In4 Fig. 22, which 'shows diagrammatioally the two operating mechanism (omitting the bleed lines and locker), the unit Sli-has applied to it the reference numbers of Fig. Sand-the unit 3| has' the sam'e numbers with primes. Pressure has been applied from the control valve to the line begins to act upon the valve I5 against its additional resistance of 250 p. s.i

From the pressure values assumed in the wiper When the control valve reverses, the line 43- becomes an exhaust line, and pressure is applied to the line 42 to move the wipers back. At such time, the oil between the pistons, including that .in the line 44, will remain practically undiminished. Therefore, both wipers wil-l move back in synchronism. At the end of this reverse stroke, both valves and 15 will be urged open simultaneously, offering their combined resistance of 50o-p. s. l., and the control valve will again reverse.

During continued operation, the two valves 'I5 and 'I5' may open only as necessary to keep the oil supply between the pistons full.

42 and the line 42 has been connected to the y exhaust.

The pressure oil iiowing into the right end of the cylinder 49 will have acted against the piston Il. and will have applied pressure .to the right end of the valve 15. 'Ihe resistance of the springs Il and 8|, and the-springs 80 and 8l', is greater than the normal resistanceof the wipers and the mechanism in regular operation. For instance, the valves 'I5 and-15 may. have a resistance of 250 p. s. i. Hence, the entire piston Il will have moved to the left to the end of -its stroke. When the-piston is stopped, the resistance goes quickly beyond the 250`p. s. i., and the valve 'Il will have been forced tothe left, permitting oil to ilow through the piston, into the line 44 and against the piston 6U', moving it to the left, until it has reached the position shown in Fig. 22.

Atthis point the pressure again' rises. It must be above 250 p. s. i. vto have held the valve 'I5 open. When the piston 80' stops; the pressure vThe foregoing values are only typical. The

Acritical factors are to have the combined ordinary operating resistances of the wipers plus that of all of the valves I5 except one, less than the resistance of the valve IIIl, but to have the combined resistance of all valves l5 and 15' greater than that of the valve IIO. Pressures in values obviously rmeans pressure diierentials between the high pressure and low pressure sides.

It will be observed by referring to Fig. 5 that a dashpot action is provided at each end of the stroke of each piston. For example, as the piston 60 moves to the left in Fig. 5. at the end ot its stroke, the projection B'I will begin its loose engagement in the smaller cylindrical portion 52. This will mean that a quantity of oil is retained between the cylinder head and the piston head, which is checked by the seating of the ball 56.

This trapped oil can escape only around the loose llt of the portion 61 in the dashpot action is provided. relieved to permit the piston the cylinder head by the moving of the check ball 56 from its seat.

As has been noted, the plunger 89 is adapted to lock the pistons ineither of their `extreme positions. If the pistons are locked at the start of any cycle of operation, one of the slots 91 or |00 will be in registry ywith either port 9S or 99, respectively. l Assume the pistons areat the right as shown in Fig. 5. If upon restart, pressure returns through the line 43, it will ow through the port 96 to depress the plunger '89. It will also displace the valve 15, ilow through the line 44, and act to depress the locking plunger in the other piston. After this has occurred, its further effort to displace the other valve 15 will result inreversal of the control valve. But the check valves will retain the oil againstthe plunger 89 so that they will be held down, and the supply of oil for such purpose is renewed at the end of each stroke.

If thestart occurs with the pressure introduced to the right ends of the pistons (as in Fig. 5), oil will ilow 'through the valves i5 of the rightmost piston, and then back to release portion 52. Thus, a This. of course, is

its locking plunger, prior to displacing the other valve 'l5 to reverse the lcontrol value. Reversal o! the control valve introduces pressure to the to move away fromv tons.

, 9 f left end of the other piston, which will unlock it. Finally, on an additional reversal. the wipers will start.

It is readily apparent how unlocking will occur if only one wiper is locked. j

The relief groove 86 extends around the piston. It is always in communication with one of the ball valves, and thereby readily releases any pressure that might build up around the ywiper shaft, as these valves have relatively light resistance. The disposition of the detent notches 81 and B8 in this groove prevents scraping of the cylinder by any burs on their edges that might be turned up bythe detent plunger.

When the main speed control valve 34 is closed. the pressure acting against the piston 89 will gradually bleed around the upper part of the piston and through the opening in the top thereof to relieve itself through the line 40. Also pressure on one or the other sides of the piston 80 will gradually relieve itself around the piston and into the tube I0. When the piston 89 is relieved, it will move into one of the notches 81 or 88 and will lock the wipers in position until they are turned on again. This is a mechanical lock. It will be observed that this mechanical lock can be relieved whenever pressure is built up enough through one of the notches 91 or i to force back the piston. The resistances of the two pistons and two of the check valves are less than the pressure necessary to shift the selector valve.

An adjustment of the cut-on valve 34 alters the speed with which the various pressures can be built up, and, therefore, it varies the speed of operation of the entire mechanism.

If one of the wipers is blocked, as by slush or ice, the other will operate through its complete cycle, and the blocked one will operate through the sweep permitted by the obstruction. If both are blocked, they will sweep through the stroke permitted. This comes about because a blocking of one wiper unit limits the movement of its piston with the same eect on the pressures as if the piston had reached the end of its stroke. The resistance ofthe two units in series in whatever positions they -are stopped will become greater than the displacing resistance ofthe selector valve, and the mechanism will reverse. It will also be seen that the wiper will strike against the obstruction with some force and may clear it away by repeatedly beating it.

If the wipers become desynchronized, they will always resynchronize. If an obstruction oi'- one occurs, such as when 30 ismoving to the right in Fig. 22, and when the connecting line 44 is filled with oil, the piston 60' will, nevertheless, move its full stroke even though the piston 60 be blocked. This will force some of the oil normally trapped within the line 44 through the valve 15. But it will be observed, that, at this time, the other valve is not operating, so that the force required is the force to overcome only one of the valve resistances plus the force to move the piston. Not until the piston '6B reaches the end of its stroke, will both valves be put in series.

Thereafter, upon a reversal, the piston 60 will move more quickly to its left-hand extreme, but

such motionwill be insuilicient to displace the l quantity of oil required to move the piston 60' to its left-hand extreme owing to the previously mentioned reduction of oil between the two pis- Then the valve 15 will be displaced until the piston Ell is moved to its left-hand limit. After this last situation is produced, the valve 1B' will be put in series with the valve 1l. and a reversal will occur, but, at this time, resynchronization has already occurred.

If one of the wipers becomes permanently blocked in a iixed position the other wiper will continue to operate through its full permitted stroke. Also, both wipers may operate on a limited stroke or one in a stalled, and the other on a limited stroke. In every case,` resynchronization is automatic.

The number of wiper units used can be multiplied indefinitely. It is necessary only to have the total resistances of all of the valves 15 in series greater than the neutralizing force on the selector valve lill, but with any less than the total number less than the neutralizing force on the valve lili.

The mechanism can be used with one wiper, as the unit 30, in which case, when the piston 60 would stop, the control valve would shift. Advantages of operating a. single wiper this way are that it would not require a full stroke to reverse itself, and that it would have the beating action tending to break down any obstructions to its cycling for its full'sweep.

What is claimed is:

1. In a mechanism of the kind described, a plurality oi windshield wiping units adapted to wipe back and forth. oppositely operable fluid pressure means including opposite fluid connections adapt.- ed to receive pressure oppositely for so operating them, means to connect said fluid pressure means in series in a reversible iluid pressure circuit, means to control the iiuid pressure means to apply iiuid under pressure thereto first in one direction and then in the other, each of said units including means to resist the fluid under pressure with a maximum resistance when the unit is stopped, and said control means being operable in response to the total maximum pressure resistances to reverse the flow oi'. fluid under pressure when all of said units are stopped. but being inoperable to reverse the flow of such fluid when less than all of the units are stopped.

2. In a mechanism of the kind described, a plurality of wiper umts, each' unit having a fluid chamber within which is a power member adapted to move in opposite directions, fluid -pressure means for controlling application of fluid lunder pressure to opposite sides of said power members to eilect back and forth movement of the wiper units, said fluid pressure controlv means being operable upon existence of predetermined iluid pressure to reverse the flow of fluid under pressure from one side to the other of said power members, said fluid chambers being connected in series whereby iluld must pass from one to the other for operating the wipers, fluid flow resisting means normally preventing iow of iluid from one chamber to another, but resistingly permitting such flow, the resistance thereof being greater than the normal operating resistance of the unit,

but less than the resisting pressure of the power member when stopped, and the sum of the reslstances thereof for all the units being greater than the reversing force for operation of the control means, but the sum of less than all of said resistances being less than the reversing force necessary for operating the control means.

3. In a mechanism of the kind described, a wiper element including a pressure chamber, a pressure-responsive member in th'e chamber adapted to be displaced in opposite directions in the chamber in response to application of fluid under pres- Sure t0 one end or the -other of the chamber,

Vtion to close th'e means limiting movement oi' the member in eaching resistance greater than the normal operating resistance oi' the pressure-responsive memberbut less than the iluid pressure when the pressureresponsive member has stopped moving.

4. In a mechanism of the kind described, a plurality of fluid-pressure operated windshield wiper umts, each including a cylinder and a .piston therein, a tube connecting the chambers of said wiper units in series, by-pass means to permit ilow oi' iluid from one chamber to the next, resistingly yieldable valve means controlling said by-pass means and operable upon existence of predetermined pressure conditions in the chamber, a control including a valve subjected to pressure into the chambers, resisting means adapted to hold against pressures as great as al1 but one of said resistinly yieldable by-pass valves but adapted to yield to pressures of all said by-pass valves in series, said resisting means being adapted to oppose displacement oi.' the control valve. and th'e control valve, when displaced in response to such pressures, being adapted to institute a reversal of application oi' fluid under pressure from one end 'of said chambers to the other, to reverse the wiper units.

5. In a mechanism of the kind described, a windshield wiper unit including a cylinder and a piston oppositely displaceable therein, wiper mechanism operated by the piston. iluid passage means into opposite ends of the cylinder, means to introduce pressure uid alternately into the ends of the cylinder to eilect displacement of th'e piston, resisting by-pass means adapted to bypass the fluid from one end to the other of the piston, including passage means between the ends of the cylinder and yieldable means resisting communication through the by-pass, whereby said by-pass means is adapted to introduce iiuid from the ilrst end into the second end, pressure in the iluid inthe rst end, the resistance of th'e by-pass means being greater than the operating resistance of the piston and parts displaced thereby.

6. In a mechanism oi the kind described, a plurality of nuid pressure operated umts, each including a cylinder, a piston oppositely displaceable therein, mechanism operated by movement of the piston in opposite directions, a port adapted to establish communication from one side of the piston to the other to introduce iluid from one side to the other. a valve controlling th-fport, yieldable means maintainingthe valve in posiport, but yieldable to open the same upon application of predetermined pressure to either side thereof, the resistance oi' said yleldable means being greater than the normal resistance to displacement of the piston and mechanism operated thereby,` means to connect the cylinders in series, and means to interpose theries in a pressure-reversing uid pressure c rc predetermined ment operated by comprising a valve "1. In a mechanism oi the kind described. a plurality ol' uid' pressure operated units, each including a cylinder, a piston oppositely displaceable therein, mechanism operated back and i'orth by reciprocation oi th'e ton from one 'side to the other thereof, a valve in the piston having a closing position with respect to the portfand being adapted for displacement in either direction to open said port, a spring on each side of the valve to resist its opening in each direction. the resistance ailorded by ach .spring being Ereater than the normal operating resistance o: the piston and mechanism operated thereby, means to connect the cylinders in series. and means to interpose the series in a pressure-reversing duid pressure circuit.

8. In a windshield wiper mechanism, a windshield wiper unit comprising a chamber, a pistonlike-member movable in the chamber, a wiper elethe piston member, openings into th'e opposite sides of the chamber, a pressure control having a iluid pressure inlet and an outlet, a pair oi fluid-pressure lines connected respectively to the opposite openings in the chamber, and pressure-responsive means selectively to connect one oi.' said lines to the inletand the other to the outlet and'vice versa. said means comprising a directional valve adapted to be moved to eilect connection of the rst line to the inlet and the second to the outlet, and vice versa, said directional valve being adapted to be moved by application of pressure oppositely thereon, and selector valve means movable for admitting pressure selectively in one of two lines in accordance with the position of the selector valve means, said selector valve means being connected to receive the high pressure as it is applied to the fluid-pressure lines. for displacement thereof in accordance with pressure conditions oi said lines. force means resisting displacement of the selector valve means, and permitting displacement of the selector valve means only when the pressure oi.' the respective duid-pressure line attains a predetermined value, and means responsive to the pressures in said two selector valve lines to eect shifting of the directional valve to its other position reversing pressure connections of said lines.

9. In a windshield wiper mechanism, a windshield wiper unit comprising a chamber, a pistonlike member movable in the chamber, a wiperelement operated by the piston member, openings into the opposite sides of the chamber, a pressure control having a iluid pressure inlet and an exhaust outlet, a pair oi' fluid-pressure lines connected respectively to the opposite openings in the chamber, and pressure-responsive means selectively to connect one oisaid lines to the inlet and the other to the outlet and vice versa, said means adapted to be moved to eiIect connection of th'e iirst line to the inlet and the second to the outlet, and vice versa, means controlling the position of said valve comprising mechanism movable in opposite directions from a neutral position in response to pressure changes oppositely acting thereon, yieldable means urging thesame into neutral position, ports connecting opposite sides of the mechanism with the respecv tive lines, whereby said mechanism responds to pressure conditions thereof, said yieldable means resisting displacement until the pressure in one of the lines receiving uid under pressure attains a predetermined value, and means operated to reverse the valve upon displacement oi the mechanism.

10. In a windshield wiper mechanism, a windpiston, a port through the pisshield wiper unit comprising a chamber, a pistonlike member movable in the chamber, a wiper element operated by the piston member, openings into the opposite sides of the chamber, a pressure control having a fluid pressure inlet and an exhaust outlet, a pair of fluid-pressure lines connected respectively to the opposite openings in the chamber, and pressure-responsive means selectively to connect one of said lines to the inlet and the other to the outlet and vice versa, said means comprising a valve adapted to be moved to effect connection oi the first line to the inlet and the second to the outlet, and vice versa. means controlling the position of said valve comprising mechanism movable in opposite directions from a neutral position in response to pressure changes oppositely acting thereon, yieldable means urging the same into neutral position, ports connecting opposite sides of the mechanism with the respective lines, whereby said mechanism responds to pressure conditions thereof, said yieldable means resisting displacement until the pressure in one of the lines receiving fluid under pressure attains a predetermined value, and means operated to reverse the valve upon displacement of the mechanism, said last-named means comprising a second valve operable into two positions, in one of which it connects one side of the first valve to pressure and the other side to exhaust, and vice versa in the second position, means operating the second valve to one position or the other in respouse to the operation of the mechanism from its neutral position one way or the other, and means insuring complete operation of the second valve by the time the first valve has shifted to eiectively reduce the pressure acting to shift the mechanism.

i 11. In a windshield wiper mechanism, a windshield wiper unit comprising a chamber, a pistonlike member movable in the chamber, a wiper element operated by the piston member, openings into the opposite sides of the chamber, a pressure control having a fluid pressure inlet and an exvso haust, a pair of fluid pressure lines connected respectively to the opposite openings in the chamber, and means selectively to connect one line to the inlet and the other to exhaust, and vice versa, said means comprising a first valve displaceable to eiect said connections selectively, and opposite pressure means adapted selectively for connection to uid pressure or exhaust for displacement of said first valve, a second valve controlling said opposite pressure means of the first valve, the second valve being displaceable to connect selectively one side of said means to pressure and the other to exhaust, and vice versa, means restricting i the duid Iflow around said second valve to said opposite pressure means of the rst valve to delay `action of the latter, opposite fluid pressure means adapted selectively for connection to fluid pressure or exhaust for displacement of the second valve, a third valve having opposite pressureresponsive operating means connected to the fluid pressure lines and under control of the first valve, yieldable means urging the third valve into neutral position, said third valve being adapted to be displaced by admission of fluid under pressure to its opposite pressure means and building up of said pressure to predetermined values exceeding the resistance of said yielding means, said third valve, upon such displacement, being adapted to connect the pressure means of the second valve to pressure and exhaust to reverse the second valve, said connection being free to cause rapid movement of the second valve, whereupon the secshield wiper unit comprising a chamber, a pistonlike member oppositely movable in the chamber,

a wiper element operated by the piston-like member, openings into the opposite sides o: the chamber, a pressure control having a fluid pressure inlet and an outlet, a pair of fluid-pressure lines connected respectively to the opposite openings into the chamber, and pressure-responsive means selectively to connect oneof said lines to the inlet and the other tothe outlet and vice versa, said means comprising a directional valve adapted to be moved to effect connection ofthe first line to the inlet and the second to the outlet, and vice versa, said directional valve being adapted to be moved by application of pressure oppositely thereon, and selector valve means movable for admitting pressure selectively in one of two lines in accordance with the position of the selector valve means, said selector valve means being connected to receive the high pressure as it is applied to the fluid-pressure lines, for displacement thereof in accordance with pressure conditions of said lines, force means resisting displacement of the selector valve means, and permitting displacement of the selector valve means only when the pressure in the respective' fluid-pressure line and the side ot the chamber connected therewith attains a predetermined value, and means responsive tothe pressures in said two selector valve lines to effect shifting of the directional valve toits other posi-A tion reversing pressure connections of said lines,

said last means including a pilot valve interposed f plurality of fluid pressure operated units, each l including a cy1inder, a piston oppositely displaceable therein, mechanism operated by movement of the piston in opposite directions, a port adapted to establish' communication from one side of the piston to the other to introduce fluid from one side to the other, said port comprising a passage of predetermined length, a valve controlling the port, said valve comprising a slidable member having a shape conforming to that of said port. a notch extending from one end of the valve toward the other but terminating short of the said other end, a similar notch extending from said other end toward said one end, but terminating short of the same, whereby when said valve is in a mid-position the port` is closed, and when it is displaced in either direction the port is opened, yieldable means maintaining the valve in position to close the port, but yieldable to open the cylinders in series, and means to interpose the series in a pressure-reversing iluid pressure circuit.

14. In a mechanism of the kind described, a

l plurality of units adapted to operate back and forth between normal liimts, means to apply a force to operate said units in series, each of said units offering a resistance to movement that increases when the unit is stopped, said forceapplying means including a reversing mechanism through which the force is transmitted to the units in series, said reversing mechanism including force-responsive means to eil'ect reversal ot the force, said force-responsive means having a resistance means with a resistance greater than all but oneof the umts stopped, but less than that of al1 of the' units stopped.

15. In a, windshield wiper mechanism, a' windshield wlper unit including a chamber having a piston-like member therein.- a wiper unit connected to th'e piston-like member, a reversing mechanism for use with a high iluid pressure line and a low iluld pressure line, a rst and a second port connected with the opposite ends o! the chamber and adapted to be respectively connected to the high and the low pressure lines, and vice vesra, a directional valve movable to determine which of the connections shall be made, a pilot valve movable for controlling movement of th'e directional valve, means responsive to pressure in the port connected with high pressure, to effect movement of the pilot valve to reverse the position of the directional valve `upon attainment of a predetermined pressure in the high pressure port and the side of the chamber communicating therewith, and means to insure full movement of the pilot valve by the time the directional valve has moved.

16. In a windshield wiper mechanism, a wiper unit having a chamber and a piston-like member therein, the chamber having openings on opposite sides of the member, a. wiper unit operated by the piston-like member, a pressure control having a iluid pressure inlet and an exhaust, a pair of iluid pressure ports connected respectively to the opposite openings of the wiper unit chamber,` and means selectively to connect one port to the inlet and the other to exhaust, and vice' versa, said means comprising a ilrst valve displaceable to effect said connections selectively, and opposite pressure means adapted selectively for connection to fluid pressure or exhaust for displacement of said first valve, a second valve for controlling said opposite pressure means of said ilrst valve, the second valve being displaceable to connect selectively one side of said means to pressure and the other to exhaust, and vice versa, means restricting the iluid ilow around said second valve to said opposite pressure means oi the ilrst valve to delay movement of the latter, opposite iiuid pressure means adapted selectively for connection to iluld pressure or exhaust for displacement of the second valve, iluid pressurel responsive means to connect the opposite pressure means of the second valve to pressure and exhaust, respec tively-and to reverse said connections, said connections for operation of the second valve being relatively unrestricted to insure full operation thereof at least by the time the rst valve has been moved. v

17. In a windshield wiper, a wiper unit having a chamber and a piston-like member therein, the chamber having openings on opposite sides of the member, -a Wiper unit operated by the piston-like member, a pressure control having a fluid pressure inlet and an exhaust, a pair of fluid pressure pressure or exhaust for displacement of said iirst valve. a second valve for controlling said opposite pressure means of said .first valve, the second valve being displaceable to connect selectively one side ot said means to pressure and the other to exhaust, and vice versa, means restricting the iluid ilow around said second valve to said opposite pressure means of the rst valve to delay movement of the latter, opposite uid pressure means adapted selectively for connection to iluid ports connected respectively to the opposite openings of the wiper unit chamber, and means selectively to connect one port to the inlet and the pressure or exhaust for displacement of the sec` ond valve, iluid pressure responsive means connected to said fluid pressure ports whereby to operate when the fluid pressure in the port connected with high pressure attains a. predetermined value, and passage means valved by the iluid pressure responsive means for selectively connecting one of the opposite pressure means of the second valve to high pressure and the other to low pressure, and vice versa, whereby the second valve will be moved upon attainment of the predetermind pressure in the high pressure port, and means to yprevent movement of the rst valve to relieve the high pressure port until the second valve has been moved.

18. In a mechanism of the kind described, a plurality of reversible operating units, each unit having a fluid chamber within which is a power member adapted to move in opposite directions, iluid presssure means for controlling application of uid under pressure to opposite sides of said power members to eiect back and forth movement of the units, said iluid pressure control means being operable upon existence of predetermined Iluid pressure to reverse the flow of uid under pressure from one side to the other of said power members, said iluid chambers being connected in Aseries whereby uid must pass from one to the other for operating the units, iluid iiow resisting means normally preventing iiow of i'iuld from one chamber to another, but resist; lngly permitting such iiow, the resistance thereof being greater than the normal operating resist. ance of the unit, but less than the resisting pressure of the power member when stopped, and the sum of the resistances thereof'for all the units being greater than the reversing `force for operation of the control means, but the sum of less than all of said resistances being less than the reversing force necessary for operating the control means.

19. In a, mechanism of the kind described, a plurality of fluid-pressure operated reversible units, each including a chamber and a piston therein. a tube connecting the chambers of said umts in series, by-pass means to permit ow o1' uid from on-e chamber to the next, resistlngly yieldable valve means controlling said by-pass means and operable upon existence of predetermined pressure conditions in the associated chamber, a control including a valve subjected to pressure admitted into the chambers, resisting means adapted to hold against pressures as great as all but one of said resistlngly yieldable by-pass valves but adapted to yield to pressures of all said by-pass valves in series, said resisting means being adapted to oppose displacement of the control valve, and the control valve, when displaced in reponse to such pressures, being adapted tc institute a reversal of application of fluid under pressure from one end of said chambers to the other, to reverse the units.

20. In a mechanism of the kind described, a plurality of Wiper units comprising resisting but yieldable pressure-receiving elements inserted in series in a pressure line, and oppositely movable in response to pressure applied from opposite ends of the line, said elements having greater resistance when stopped than when moving, a resistance-responsive control means to cause application of pressure to the elements in series, first in one direction and then in the other, to operate the Wiper units back and forth through a given maximum cycle, said means including reversing means operable in response to resistance of all units stopped, but inoperable to effect reversal in response to resistance of less than all units, and said control being thereby adapted to operate all umts until all are stopped, whether or not at the end of their strokes, and then to reverse them.

21. In a mechanism of the kind described, a windshield wiper unit including a chamber and a piston-like member movable back and forth therein, wiper mechanism operated by the member, a fluid connection into the chamber on each side of the piston-like member, whereby uid under relatively high pressure may be alternately introduced into the opposite sides of the chamber to move the piston-like member and wiper mechanism, pressure-resisting by-pass means supplemental to the fluid connections, adapted to byps the uid und-er pressure from one side to the other of the piston-like member, including passage means between the ends of the chamber. and yieldable means resisting flow through the passage means, whereby said by-pass means is adapted to admit uid from the high pressure side to the low pressure side of the piston upon existence of a predetermined pressure condition in the uid, the resistance of the yieldable means being greater than the normal operating resistance of the piston-like member and the parts displaced thereby.

22. In a'` mechanism of the kind described, a windshield wiper unit including a chamber and a, piston-like member movable back and forth therein, wiper mechanism operated by the member, a iiuid connection into the chamber on each side of the piston-like member, whereby fluid under relatively high pressure may be alternately introduced into the opposite sides of the chamber to move the piston-like member and wiper mechanism, pressure-resisting by-pass means supplemental to the fluid connections, adapted to bypass the uid under pressure from one side to the other of the piston-like member, including passage means between the ends of the chamber, yieldable means resisting flow through the passage means, whereby said by-pass means is adapted to admit fluid from the high pressure side to the low pressure side of the piston upon existence of a predetermined pressure condition in the fluid, the resistance of the yieldable means being greater than the normal operating resistance of the piston-like member and the parts displaced thereby, and control means for alternatively controlling the introduction of uid under pressure to the opposite sides of the chamber, including a fluid pressure-responsive reversing device subjected to the pressure of the operating fluid operable to reverse the pressure application from one side to the other when the high fluid pressure rises by stoppage of the piston-like member to a predetermined value.

23. A windshield wiper unit comprising a cylinder ported at opposite ends, a piston reciprocable in `the cylinder, the piston having a passage therethrough, valve means to close said passage, said valve means being adapted to be subjected to fluid under pressure from either side of the pis- REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 885,459 Engler Apr. 21, 1908 1,268,912 Baader June 11, 1918 1,569,143 Robinson Jan. 12, 1926 1,677,860 Ferris July 17, 1928 1,952,690 Strom Mar. 27, 1934 2,033,839 Lawson Mar. 10, 1936 2,060,684 Moorhouse Nov. 10, 1936 2,100,445 Le Bleu Nov. 30, 1937 2,221,313 Lawrence Nov. 12, 1940 2,266,867 Hume Dec. 23, 1941 2,270,943 Freundel Jan. 27, 1942 2,298,457 Berges Oct. 13, 1942 2,302,232 MacNeil Nov. 17, 1942 2,370.37 6 Snell Feb. 27, 1945 

